1. Field of the Disclosure
Embodiments disclosed herein relate generally to mud saver valves for saving drilling fluid. In particular, embodiments disclosed herein relate to a mud saver valve in a drillstring for saving drilling mud in the upper drillstring while a new drill pipe connection is made below the mud saver valve.
2. Background Art
During well drilling operations multiple joints of drill pipe may be added to a drillstring by first disconnecting an upper portion of the drillstring and then installing a new piece of drill pipe between the disconnected upper and lower portions of the drillstring. During such a connection procedure (“make-up”) or during a similar disconnection procedure (“break-out”), drilling fluid or mud within the upper drillstring may be lost unless some type of valve apparatus closes off the upper drillstring to hold drilling mud therein. One device that may be used to close off fluid flow through the upper drillstring is a mud saver valve, which is between a kelly (a component used to transmit rotary motion from the rotary table to the drillstring) and the upper portion of the drillstring. The mud saver valve operates in response to drilling fluid pressure, i.e., the mud saver valve may be closed when mud pumps are turned off and opened when the mud pumps are again turned on. Within the mud saver valve, an upper seat (typically a rubber seat) and a lower seat (typically a carbide seat) are configured to move into and out of sealing contact in response to these changes in drilling fluid pressure.
A typical size for mud saver valves used in drilling operations may be a 6½ inch mud saver valve. The 6½ inch valve may provide a streamlined fluid flow path, reduced localized velocities near the upper and lower seats in the mud saver valve, and increased run time of more than 30 days before required service. Smaller mud saver valve sizes are also available, particularly a 4¾ inch valve size. However, smaller valve sizes have experienced problems with erosion near the rubber upper seat due to increased fluid velocities in the upper seat region. Erosion of the rubber upper seat has reduced the service life of the smaller mud saver valves, thus requiring increased maintenance and downtime.
Accordingly, there exists a need for an apparatus to reduce or prevent erosion of the upper rubber seat in smaller mud saver valve sizes.